The invention relates to a grid cooler, particularly of the type which may be termed a feed step grid cooler with cooling opening therethrough so that cement clinker falling on the grid moves forward on the inclined grid and is cooled thereon.
Feed step grid coolers of this type include alternately stationary and movable perforated grid elements where the air flows upwardly through the heated material on the upper surface. Rows of stationary grid plates are fixedly connected with a base of the cooler housing. Movable rows of intermittent grid plates are supported on the housing and driven by an eccentric drive usually installed outside of the base of the housing. Inasmuch as the grid is inclined, oscillating movement of the movable rows of grid plates cause the material to be cooled to flow down over the surface of the cooling grid while air moves upwardly through the material, and the material is received at the receiving or upper edge of the grid and is discharged at the lower or discharge edge of the grid onto another grid.
It has been a practice before to support several cooling grids consecutively in a cooler housing and to construct the first cooling grid in an inclined manner as, for example, as shown in German Pat. No. 1,170,307. It has also been a practice to provide different feeding speeds to the individual cooling grid in order to produce a different thickness in the bed of the material to be cooled. This method of regulation of cooling is utilizable to a limited extent. It does not take into account fluctuations in the average granular size of the material to be cooled as occurs in the case of cement clinkers. Accordingly, when the average clinker size is altered by virtue of altering the calcining operations and the cement clinker grain size becomes substantially greater or smaller, the flow behavior of the material on the grid changes. In addition other qualities which affect either the flow behavior or the cooling effect of the air moving up through the material will occur which are not controllable to attain the proper cooling solely through alteration of the speed of feed of the material.
An arrangement which has been attempted for control of flow behavior of cement clinker on inclined grid cooler has been to curve the feed edge of the grid plates upwardly so that the grid plates are approximately synclinal, as shown in German Pat. No. 952,785. With this more expensive arrangement, the height of the clinker bed on the cooling bed, however, does not permit itself to be adjusted to optimum depth.
It is an object of the present invention to provide a simplified and improved grid cooler in which the depth of the material bed located on the cooling grid is optimumly adjustable even with greatly fluctuating character of the granules of the material and type of material being received from the kiln.
A further object of the invention is to provide an improved grid cooler which meets the foregoing objective and where the entire cooling grid inclination can be changed without adversely affecting the other operating qualities of the grid.
In a grid cooler constructed and operating in accordance with the principles of the present invention, the stationary grid plates are no longer connected fixedly with the base portion of the housing of the cooler as they were heretofore, but the cooling grid as a whole is changed by raising or lowering the grid plate about a pivotal axis which is located coincident with the upper surface of the discharge end of the grid. The angle of incline of the grid can be changed from a horizontal or slightly inclined material feed plane to one which has a substantial inclination. With this construction, adaptations can be made during operation even with a substantially fluctuating character of clinker grain size and the height of the clinker bed on the cooling grid is adjustable to its optimum depth in such a manner that the cooling air absorbs as much heat as possible from the hot clinker. If the clinker grain is finer and the clinker material flow more rapidly or more strongly on the grid then the angle of inclination can be diminished. Similarly, if the clinker becomes more coarse and the clinker flow reduces, the angle of inclination can be increased. Changing charging mixture of clinker through the grid cooler are similarly more easily controllable in accordance with the principles of the invention. The mechanism for control or regulation of the speed of feed of material onto the cooling grid then is not necessary and its size and expense may be eliminated. However, in some instances, such control may be incorporated with the principles of the present invention to obtain an even greater optimum performance of the clinker cooling mechanism.